Tpddl Report.docx

A Summer Internship Report On

TATA POWER-DELHI DISTRIBUTION LIMITED

Submitted in partial fulfillment for the award of the degree of

BACHELOR OF TECHNOLOGY In Electrical & Electronics Engineering (24 May 2016- 22 June 2016)

Submitted by :Mohit Kumar 130906306

MANIPAL INSTITUTE OF TECHNOLOGY MANIPAL 1

TO WHOMSOEVER IT MAY CONCERN

I hereby certify that MOHIT KUMAR roll no. 130906306 of Manipal Institute of Technology, Manipal undergone 4 weeks Summer Internship from 24 May 2016 to 22 June 2016 at our organization to fulfill the requirement for the award of degree of B.TECH Electrical & Electronics Engineering. During his tenure with us we found him sincere and hard working. We wish him a great success in the future.

Signature of mentor Dushyant Kr. Tyagi

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Acknowledgement

“Every good work requires the guidance of some experts” I am very thankful to Tata Power Delhi Distribution Limited for having given me the opportunity to undertake my Summer Training. The satiation and euphoria that accompany the successful completion of the project would be incomplete without the mention of the people who made it possible. I would like to take the opportunity to thank and express my deep sense of gratitude to my corporate mentor Mr. Dushyant Kumar Tyagi (District Manager, CVL Lines, Tata Power Delhi Distribution Limited) for allowing me to go through the training under his guidance. This training has provided me a great experience and knowledge about the maintenance and working of the company. It would not have been possible without his help. This research was supported by him. I would also like to express my sincere thanks to Mr. Manmeet Singh, Mr. Ankush Arora, Ms. Priyanka Yadav, Mr. Chichendra Pal, Mr. Sachin Tiwari for their cooperation and encouragement during the training program. I owe my wholehearted thanks and appreciation to the entire staff of the company for their cooperation and assistance during the course of my project. I hope that I can build upon the experience and knowledge that I have gained and make a valuable contribution towards this industry in coming future.

Lastly, I express my thanks to Manipal Institute of Technology (MIT) for providing me with this unique opportunity to train for four weeks.

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TABLE OF CONTENTS 1. About the Organization 1.1 TPDDL 1.2 Name of district with corresponding zones 1.3 BU-CVL Line (Zone 418&411) 2. The Project 3. Introduction 3.1 Equipments used in Distribution System 3.2 Preventive Maintenance 3.3 Checklist of Different Equipments 4. Maintenance Philosophy 5. Survey Report 6. DT Health card 7. Testing Equipments 7.1 Tools & Testing Equipments 8. Safety while Maintenance 9. Earthing

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1. About the Organization 1.1TATA POWER DELHI DISTRIBUTION LIMITED:-

Tata Power Delhi Distribution Limited (TPDDL) was initially known as the North Northwest Delhi Distribution Company and subsequently renamed North Delhi Power Limited. In 2011, nine years after it first started operations, its name was changed once again to Tata Power Delhi Distribution Limited is a joint venture between the Government of the National Capital Territory (NCT) of Delhi and Tata Power Co. Ltd.. A 51% majority stake in the venture is held by Tata Power. It started operations on 1 July 2002 and currently serves 6 million people in the North and North-west parts of Delhi. It has a registered consumer base of 1.40 million. The company’s operations span an area of 510 sq. km. with a recorded peak load of around 1704 MW. The company’s distribution automation project is based on systems such as SCADA (Supervisory Control And

Data

Acquisition), GIS(Geographical

Information

System), OMS (Outage

Management

System), DMS (Distribution Management System) and OT’s (Operation Technologies). The SCADA controlled and unmanned grid stations, GSM based Street Lighting System, SMS based Fault Management System and Automatic Meter Reading employed by the company are all firsts in the capital city area. Modern technologies such as High Voltage Distribution (HVDS) System and LT Arial Bunch Conductor are also being used by them to curb power theft in the region. Tata Power Delhi Distribution Ltd is the first Indian utility to develop and set up Geographical Information System which has seamless integration with SCADA, SAP-ISU and Fixed Asset register. This system has unique mechanism of asset management, complaint management, network planning, etc. Tata Power Delhi Distribution Ltd. is documented as the first in the country to initiate an Automated Metering Infrastructure based Auto Demand Response programme to help manage grid stress and peak demand. This is part of the company’s Smart Grid Journey It carries a successful case study of PPP Model in Indian Power Sector and is acknowledged at national and internal forums for its contribution in bring reforms at massive scale.

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The company is the only Indian Utility member at Global Intelligent Utility Network Coalition (GIUNC) which is responsible to develop a smart infrastructure across the globe. It is also a Greening Agency within the Department of Forest and Wildlife, Government of Delhi. Its CSR initiatives include women literacy and vocational training, child education, health awareness and medical camps, drug-de addiction camps, improving basic amenities, tree plantation and sensitization programmes for the issues of climate change and environment conservation. TPDDL has touched lacs of lives through these initiatives. Solar power generation has been a part of their sustainable initiative since 2008 The Tata Power Delhi Distribution Ltd. has received numerous accolades both at the national and international level. It has won the prestigious Edison Award twice – in 2008 for Innovative Implementation of GIS and in 2009 for Policy Advocacy. The Ministry of Power, Government of India has conferred on the company the 'National Award for Meritorious Performance'[5] for outstanding performance in power distribution a total of four times. It has also been selected as a case study in categories such as Power Sector Reforms and Organizational Transformation by several top management institutes, management consultants and publications. These include IIM Lucknow, IMI Delhi, TMTC Pune, McKinsey and Wall Street Journal, USA.

Challenges when it took over:-

After it began its operations in 2002, Tata Power Delhi Distribution Limited was faced with four key problems: 

More than 50% Aggregate Technical and Commercial (AT&C) losses were being recorded, made considerably worse by rampant power theft, faulty meters and open overhead networks.



The electricity supply system in the North and Northwest Delhi distribution area was extremely unreliable due to inadequate network planning and infrastructure.



No IT interface or consumer services existed. Inherited only 2 computers that too in non-functional conditions.



There was no system of consumer services, a backlog of 1,00,000 complaints when it took over.



The 5400 employees of the erstwhile Delhi Vidyut Board who were absorbed into Tata Power Delhi Distribution Limited exhibited attitudinal and cultural issues. Their working conditions were far below Tata standards.

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1.2 NAME OF DISTRICTS WITH CORRESPONDING ZONES UNDER JURISDICTION OF TPDDL

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1.3 BU-CVL LINE (ZONE-418&411) PARAMETER TOTAL NO.OF CONSUMERS KCG CONSUMERS AREA IN SQ KMS TOTAL NO. OF FEEDERS HT CIRCUIT LENGTH LT CIRCUIT LENGTH TOTAL NO. OF RMU TOTAL NO. OF LT SWITCH TOTAL NO. OF POLES(HT+LT) TOTAL NO. OF TRANSFORMER INSTALLED CAPACITY IN MVA ENERGY CONSUMPTION PER MONTH

2015-16 29354 77 NO. 12.11SQ KM 58 NO. 158.92 KM 243.46 KM 249 NO. 438 NO. 4919 NOS 474 NOS. 140 MVA 36 MU

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2. Predictive/Preventive Maintenance of Distribution Equipments in TPDDL

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3. Introduction

In today’s competitive market scenario, all types of industries are under tremendous pressure to cut down their maintenance costs, as they form a significant portion of the operation costs. The industries are forced to look for different types of maintenance of the electrical equipment rather than usual preventive maintenance being carried out at a fixed interval of time. Over the past twenty years or so, the concept of maintenance has been assuming different dimensions and changing a lot, perhaps more so than any other management discipline. The changes are due to a huge increase in the number and variety of plant equipment in the industries, which must be properly maintained. The electrical equipment with much more complex designs require new maintenance techniques and changing views on maintenance organization and responsibilities. Maintenance activities are also responding to changing expectations as follows:  Rapidly growing awareness of the extent to which electrical equipment failure affects safety of plant and personnel and the environment.  Growing awareness of the connection between maintenance and product quality.  Increasing pressure to achieve high plant availability remaining cost-effective. The changes are testing attitudes and skills in all branches of industry to the limit. Maintenance people are required to adopt completely new ways of thinking and acting, as the plant engineers and as the plant managers. At the same time, the limitations of maintenance systems are becoming increasingly apparent, no matter how much they are computerized. In the face of this avalanche of change, the industries are looking for a new approach to the maintenance to avoid the false starts and dead ends which always accompany major upheavals. Instead they seek a strategic framework which synthesizes the new developments into a coherent pattern, so that they can evaluate them sensibly and apply those likely to be of most value to them and their companies.

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3.1 EQUIPMENTS IN DISTRIBUTION SYSTEM

1. Distribution Transformer Introduction The step down transformers used for electric power distribution purpose are referred as distribution transformer. There are several types of transformer used in the distribution system. Such as single phase transformer, three phase transformer, pole mounted transformer, pad mounted transformer, and underground transformer. Distribution transformers are generally small in size and filled with insulating oil. These transformers are available in the market in various sizes and efficiencies. Major faults in transformer can cause extensive damage in terms of interruption of electricity and large revenue loss. Poor/Inadequate maintenance in the areas of oil leakage, oil quantity, and critical accessories such as tap changers, bushings and protective instruments is the main reason for transformer failure. With proper commissioning and maintenance useful life of transformer can be extended.

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2. Ring Main Unit (RMU)

Introduction

A Ring Main Unit (RMU) is a totally sealed, gas-insulated (usually SF6 ) compact switchgear unit. The switching devices can be circuit breakers, isolators or load break switch (LBS). The switching devices are also equipped with protective relaying.

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Indications on RMU

 Manometer: It indicates the gas pressure on RMU. If the indicator is in green zone then the RMU is safe to operate. If the indicator is in red zone it must not be operated.

 VPIS (Voltage Presence Indicating System): VPIS indicates the presence of voltage at the bushing of RMU. It will also indicate live cable back end at no load. The VPIS unit works on principle of capacitive divider. The 3 phase VPIS unit takes low current from high voltage a capacitive insulator that is insulation of bushings.

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 FPI (Fault Passage Indicator): It is a device which detects the passage of fault current and provides flag or blinking of LED for local indication. It is basically used to indicate the fault that has occurred in the circuit ahead of it. FPI CTs are connected at the bushings ( 3 individual CTs for 3 phases) or a single Core Balance CT (CBCT) to detect the fault current. FPI with 3 individual CTs at the bushings sense the high current during the time of fault on one or more of the three phases causing the change of state in FPI i.e. indicating a fault & FPI with CBCT sense the vector sum of the current and look for an imbalance indicating a fault on one or more of the three phases. As the fault current flows towards the source i.e. grid, it will cause to glow all the FPIs which are coming behind the faulty section (up to the 1st switching station). In other words from 1st switching station to the faulty section, all FPIs will glow whenever fault occurs in a feeder.

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3. Air Circuit Breaker (ACB)

Introduction: LT ACBs are used in the system for distribution at 415V level. The incomer cables from the distribution transformers are connected to the incoming terminals of one or more ACBs and the feeder circuits are taken out from the outgoing terminals of ACBs. The various ratings of LT ACBs presently being used are 400A, 800A, 1250A and 2000A. The technical specifications are as follows:

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3.1 FAILURE OF ELECTRICAL EQUIPMENTS

An example of electrical bralpowerassociate.blogspot.com)

equipment

failure

(photo

credit:

Failure of any electrical equipment or rather any equipment should be taken up seriously. Detailed analysis of each failure should be carried out, which will help in significant reduction of repeated failures of same nature. It is true that in spite of carrying out regular maintenance, failure of the equipment cannot be totally eliminated. Failures of different types of electrical equipment are reported by all the industries and some of the failures are quite serious resulting in substantial production losses besides causing consequential damage to the adjoining equipment as well. For example, when the equipment like surge arrestors operating at extra high voltage fail,they explode like a bomb many a times resulting in scattering of solid porcelain pieces to a larger distance causing damage to the 17

adjoining equipment. Similar situation is also observed during incident of fire in electrical switchboards due to heavy short circuit. Unless regular equipment maintenance is carried out adopting any of the maintenance systems discussed in succeeding points, unscheduled failure of the equipment would go on resulting into large scale production losses in the industries on one hand and would increase the cost of maintenance on the other hand, as the cost of breakdown maintenance is normally more than that of other types of maintenance. As technology has advanced, various maintenance strategies have evolved, including condition based maintenance, predictive maintenance, remotemaintenance, preventive maintenance, e-maintenance etc. The main challenges faced by organizations today are choosing the most efficient and effective strategies to enhance and continually improve operational capabilities, to reduce maintenance costs and to achieve competitiveness in the industry. Therefore, in addition to formulating maintenance policies and strategies for asset maintenance, it is important to evaluate their efficiency and effectiveness. Unfortunately, these maintenance metrics have been often misinterpreted and they are often incorrectly used by businesses. The metrics should not be used to show workers that they are not doing their job. Nor should they be used to satisfy the organization’s ego, i.e. to show that the company is working excellently. Performance measurements, when used properly, Should highlight opportunities for improvement, detect problems, and help find solutions.

Type of Maintenance:1. Condition based maintenance. (Planned shut Down (PSD), Unplanned Shutdown (UPSD)) 2. Predictive maintenance. (PSD) 18

3. Preventive maintenance. (PSD) 4. Emergency Maintenance. (Emergency Shutdown).

3.2 PREVENTIVE MAINTENANCE

Preventative maintenance (or Preventive Maintenance) is maintenance that is regularly performed on a piece of equipment to lessen the likelihood of it failing. Preventative maintenance is performed while the equipment is still working, so that it does not break down unexpectedly.

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3.3 CHECKLIST OF DIFFERENT EQUIPMENTS .1 Checklist for oil filled Distribution Transformer

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.

2 Check List for Ring Main Unit

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4. Maintenance Philosophy

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5. Survey report Perception Survey of Delhi Satisfaction on Power Supply

Delhi Human Development Report 2013

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6. DT HEALTHCARD

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7. TESTING EQUIPMENT  Single Phase Meter:

An electricity meter, electric meter, electrical meter, or energy meter is a device that measures the amount of electric energy consumed by a residence a business or an electrically powered device. Electric utilities use electric meters installed at customers' premises to measure electric energy delivered to their customers for billing purposes. They are typically calibrated in billing units, the most common one being the kilowatt hour [kWh]. They are usually read once each billing period. When energy savings during certain periods are desired, some meters may measure demand, the maximum use of power in some interval. "Time of day" metering allows electric rates to be changed during a day, to record usage during peak high-cost periods and off-peak, lower-cost, periods. Also, in some areas meters have relays for demand response load shedding during peak load periods.

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7.1 TOOLS AND TESTING EQUIPMENT  Torque Wrench:

A torque wrench is a tool used to precisely apply a specific torque to a fastener such as a nut or bolt. It is usually in the form of a socket wrench with special internal mechanisms. A torque wrench is used where the tightness of screws and bolts is crucial. It allows the operator to measure the torque applied to the fastener so it can be matched to the specifications for a particular application. This permits proper tension and loading of all parts. A torque wrench measures torque as a proxy for bolt tension. The technique suffers from inaccuracy due to inconsistent or uncalibrated friction between the fastener and its mating hole. Measuring bolt tension (bolt stretch) is more accurate but often torque is the only practical means of measurement. 

How To Use:

 

Apply Torque in a slow, methodical manner and avoid sudden” jerking” movements. When the wrench signals that a specific torque has been reached, Stop pulling immediately.

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 Crimping Tool:

A crimping tool is a device used to conjoin two pieces of metal by deforming one or both of them in a way that causes them to hold each other. The result of the tool's work is called a crimp. A good example of crimping is the process of affixing a connector to the end of a cable.

How does it work? To use this crimping tool, each wire is first placed into the connector. Once all the wires are in the jack, the connector with wires is placed into the crimping tool, and the handles are squeezed together. Crimping punctures the plastic connector and holds each of the wires, allowing for data to be transmitted through the connector. 

Caution: 

Select the appropriate crimping dies.



Check the die alignment.



Avoid placing excessive pressure on the dies.



Ensure the tool has sufficient, clean hydraulic oil in the piston before operation.

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 Spiking Tool : The equipment is a safety tool used for spiking the cables before execution of work on burial cables.



How to operate in spiking mode:   



Put the directional lever at forward position. Generate the pressure in the hydraulic pump by operating handle. Observe the movement of knife till desired pierce length.

How to operate in Pull-out mode:   

Put the directional lever at backward position. Generate the pressure in the hydraulic pump by operating handle. Observe the movement of knife till pull-out level.

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 Hi-Pot Set:

   

 

Connect the Hi-Pot set to 220v mains. Pull down the power knob for providing AC supply to Hi-Pot set. The POWER LED will glow. Connect the crocodile clamp of earth to the earthing strip of RMU. The earth and indicator LEDs will glow after pushing the HT ON push button if the earth is proper. Connect the chord with two crocodile clamps to HVDC terminals and tighten the screw. Connect the bigger crocodile clamp to a phase and the smaller crocodile clamp to cable earth strip. Set the timer to 5/10 minutes. Rotate the test voltage knob gradually to a maximum of 6.5KV for 11KV cable. The leakage current should be less than1mA. Same process to be repeated for other two phases. After Hi-Pot, press the HT OFF button and Pull-Off the power button.

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

Megger: Insulation resistance quality of an electrical system degrades with time, environment condition i.e. temperature, humidity, moisture and dust particles. It also gets impacted negatively due to the presence of electrical and mechanical stresses, so it has become very necessary to check the insulation resistance of equipment at a constant regular interval to avoid any fatal or electrical shock.

Working principle of Megger: 

 

The Megger is based on the principle of ohm-meter or ratio-meter. The deflection torque is produced with megger tester due to magnetic field produced by voltage and current, similarly like ohm’s Law. Torque produced by Megger varies Electrical Resistance to be measured as connected across the generator and in series with deflecting coil. Produced torque should be in the opposite direction if current is supplied to the coil.

Types of Megger: 33

These can be separated into mainly two types: 1. Electronic Type (Battery operated). 2. Manual Type (Hand operated).

 Earth Tester :

Earth testing covers the testing of earth electrodes and the measurement of soil resistivity. The instrument requirements depend on the range of applications. Ground resistance testing covers the testing of earth electrodes and the measurement of soil resistivity. The instrument requirements depend on the range of applications.

Procedure:    

2 Numbers of Earth rods are dug into the ground at a distance of 10 and 20 m from the ground. Please make sure that the rods are in a straight line. For LT earth resistance should be less than 5 ohm. For HT earth resistance should be less than 1 ohm.

 Digital Multimeter :

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 

A digital Multimeter is used to measure voltage, current (both AC & DC) The two terminals are connected across the conductor or equipment whose resistance or voltage is to be measured.

 Discharge rod :

A lightning rod or lightning conductor is a metal rod or metallic object mounted on top of an elevated structure, such as a building, a ship, or even a tree, electrically bonded using a wire or electrical conductor to interface with ground or "earth" through an electrode, engineered to protect the structure in the event of lightning strike. If lightning hits the structure, it will preferentially strike the rod and be conducted to ground through the wire, instead of passing through the structure, where it could start a fire or cause electrocution. Lightning rods are also called finials, air terminals or strike termination devices. In a lightning protection system, a lightning rod is a single component of the system. The lightning rod requires a connection to earth to perform its protective function. Lightning rods come in many different forms, including hollow, solid, pointed, rounded, flat strips or even bristle brush-like. The main attribute common to all lightning rods is that they are all made of conductive materials, such as copper and aluminum. Copper and its alloys are the most common materials used in lightning protection. 35

Procedure: 

Make sure the cable or the O/H conductor is dead (check with neon tester) before discharging.



Always use proper gloves while using discharge rod.



The resistance/corona capsule is touched at the cable terminations for discharging.

8. Safety while maintenance PERSONNEL PROTECTIVE EQUIPMENTS (PPE’s) AND DEVICES The company shall provide adequate & approved PPE’s for various jobs depending upon the hazard. The centralized procurement of PPE’s shall be made which will ensure the quality as per respective standards. PPE Guidelines:1. Use suitable protective equipment, like rubber gloves, mats, safety glasses, etc., wherever required as per instructions or wherever it provides greater safety. 2. All safety devices should be checked before starting work. 3. Safety equipment should be tested at frequent intervals to ensure that equipment would provide the safety desired. 4. Protective gears such as helmets, safety shoes, safety “Rassi-Zolis” are issued to linesmen, jointers, supervisors as applicable for personal protection and their usage is monitored. 5. It is responsibility of supervisor to ensure the usage of P.P.E.’s. 6. The P.P.E.’s shall not be carried / stored with tools etc. to avoid damage to them. 7. Any employee working on height above 8 feet from ground except working on platform should use Safety Belts / Rassi. 8. Uses only approve type of operating rods. 9. Operating Rods shall be kept as dry as possible. It should not be dropped / left lying on ground. A. HAND TOOLS 1) Many accidents results form improper use of tools and use of defective tools and equipments. Employees should use only those tools and equipment, which are in good condition, and only of the 43 purpose for which they are designed. Where proper and safe tools are not available for the work at hand, then employee shall report the fact to his supervisor. 2) Tools, which develop defects while in use, should be removed from the service, tagged and not used 36

again until brought in good condition. 3) Impact tools such as chisels, drills, hammers and wedges with mushrooms heads should not be used until they have been reconditioned. 4) Hammers, axes, shovel and similar tools should not be used if handles are loose, cracked or splintered. 5) Defective wrenches such as open end and adjustable wrenches with spread jaws or pipe wrenches with dull teeth should not be used, as they are likely to slip. 6) Pipe or other extensions should not be used on a wrench handle to increase the leverage unless the wrench is specifically designed for such an extension. 7) Portable electric tools should be equipped with 3 - wire cord having the ground wire permanently connected to the tool frame and is to be grounded at the other end. 8) Metal rules, metal tape lines or lines containing wires shall not be used around electric conductors or equipments. 9) All tools carried on trucks should be inspected each month and defective tools repaired or replaced. B. LADDERS 1. Inspect the ladder before use. 2. Ensure firm footing. 3. Secure at top or have a man at the foot. 4. Ensure correct angle (75 degree) or position ladder 1 foot out at base for every 4 feet of vertical height. 5. Ensure that the ladder rises 3 feet above landing point. 6. Face the ladder when climbing or descending. 7. Avoid make shift arrangement in lieu of ladder. 8. Ensure the rubber shoes at both arms and at each terminal. i.e. at each end. 9. Before fixing confirm that no electrically charged conductor is passing nearby. C. PROTECTIVE BARRIER (TEMPORARY) When the work is conducted along public streets or highways, pedestrian and vehicular traffic shall be warned by signs and flags by day and red lights or flares by night. Wherever necessary, signalmen should be provided. D. EARTHING DEVICES 1. Only approved earthing devices shall be used in all work. 2. Care shall be taken to maintain earthing by ensuring condition of clamps. 3. Neon line tester may be used to check the bus bar area, cables, over head conductors but prior to use it should be ensured that tester is in good condition.

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9. EARTHING DEFINITIONS:DEAD: - the term used to describe a circuit / equipment to indicate that a voltage is not applied. LIVE PART: - a conductor or conductive part intended to be energized in normal use including a neutral conductor. NEUTRAL CONDUCTOR: - a conductor connected to the neutral point of a system and capable of contributing to the transmission of Electrical Energy. EARTH GRID: - a system grounding electrodes consisting of inter connected connectors burried in the earth to provide a common ground for electrical devices and metallic structures. EARTH MAT:-a grounding system formed by a grid horizontally burried conductor / plate and which serves to dissipate the earth fault current to earth and also as equipment bonding conductor system. A. OBJECTIVES OF EARTHING The basics of safe grounding are: 1. To design and construct system that is capable to carry current under normal and fault conditions to ground. 2. The earth path should be capable of handling magnitude and duration of current as per the overcurrent protection of the system without any fire or flash or explosion. 3. Persons in the vicinity of earthed structures and installations shall not be exposed to the dangers of electrical shocks. B. GENERAL GUIDELINES FOR EARTHING An effective grounding system must satisfy the following conditions: 1. Provide a low impedance path to ground for personnel and equipment. 2. Withstand and dissipate repeated faults and surge currents 3. Provide ample corrosion allowance to various chemicals to ensure continuous service during life of the equipment being protected. 4. Provide rugged mechanical properties for easy driving of earth electrodes with minimum difficulty. 5. All non current carrying metal parts associated with installation shall:Be effectively earthed to a grounding system or mat which will limit the touch and step potential to tolerable values. Limit the ground potential rise to tolerable values so as to prevent danger due to transfer of potential through ground, earth wires, cable sheath fences, pipe lines etc. Maintain the resistance of the earth connection to such a value as to make operation of the protective device effective. C. STATUTORY STIPULATIONS 1. All medium voltage equipment shall be earthed by two separate and distinct connections. 2. As far as possible, all earth connections shall be visible for inspection. 13 39

3. Each earth system shall be so designed that testing of individual earth electrode should be possible. 4. Resistance of earth system shall conform to degree of shock protection desired. D. SAFETY PRECAUTIONS FOR EARTHING The precautions mentioned below should be adapted to the extent applicable and possible. 1) Examine earthing devices periodically and always prior to their use. 2) Use only earthing switches or any other special apparatus where provided for earthing. 3) Verify that the circuit is dead by means of discharging rod. The indicator itself should first be tested on a live circuit or proving unit before and after the verification. 4) Earthing should be done in such a manner that the persons doing the job are protected by earth connections on both sides of their working zone. 5) All the three phases should be effectively earthed and short circuited though work may be proceeding on one phase only. EARTHING OF OVERHEAD LINES All metal supports, all reinforced and pre-stressed cement concrete supports of overhead lines and metallic fittings attached thereto shall be permanently and effectively earthed. For this purpose a continuous earth wire shall be provided and securely fastened to each pole and connected with earth ordinarily at three points in every kilometer, the spacing between the points being as nearly equidistance as possible. Alternatively, each support and the metallic fitting attached thereto shall be efficiently earthed. 1. Metallic bearer wire used for supporting insulated wire of low and medium voltage overhead service lines shall be efficiently earthed or insulated. 2. Each stay wire shall be similarly earthed unless insulator has been placed in it at a height not less than 3.0 meters from the ground. EARTHING AND SHORT –CIRCUITING MAINS 1. High voltage mains shall not be worked upon unless they are discharged to earth, after making them dead are earthed, short-circuited with earthing. Short circuiting equipment is adequate to carry possible short circuit currents. All earthing switches wherever installed should be locked up. 2. If a cable is required to be cut, a steel wedge shall be carefully driven through it at the point where it is to be cut. 3. After testing the cable with DC voltage the cable shall be discharged through 2 mega ohms resistance and not directly owing to dielectric absorption, which is particularly prominent in the DC voltage testing of high voltage cables. The cable shall be discharged for sufficiently long period to prevent rebuilding up of the voltage as per the work instructions W01 (COS-P-06) ( see annexure – XII) 4. The earthing device when used shall be first connected to an effective earth. The other end of the device shall then be connected to the conductors to be earthed. 5. Except for the purpose of testing, phasing etc. the earthing and the short-circuiting devices shall remain connected for the duration of the work. 14 REMOVING THE EARTH CONNECTIONS On completion of work, removal of the earthing and short circuiting devices shall be carried out in the reverse order to that adopted for placing, that is, the end of earthing device attached to the conductors of 40

the earthed mains or apparatus shall be removed first and the other end the connected to earth shall be removed last. The conductor shall not be touched after the earthing device has been removed from it. TESTING AND RECORD 1. All earthing systems belonging to the utility shall in addition, be tested for resistance on dry day during the dry season not less than once every two years. 2. A record of every earth test made & the result thereof shall be kept by the utility for a period of not less than two years after the day of testing. 3. It shall be available to the Electrical Inspector or any officer appointed to assist the Inspector & authorized.

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Conclusion

This 4 week of my Summer Training has taught me a lot of things. It has given me an opportunity to get an exposure of the practical implementation to theoretical fundamentals. The working of a Power Distribution Company made me realize that engineering is not just learning the structure description and working of various machines but the great part is proper planning and management skills. The work experience was great, and it will definitely help me in the future.

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